The present invention relates generally to interventional radiology, and more particularly to needle guidance.
Interventional radiology (IR) permits minimally invasive diagnostic and surgical procedures. In an IR procedure, medical imaging techniques allow a radiologist (or other medical staff) to guide small surgical instruments or devices into the region of interest in a patient. Examples of medical imaging techniques include X-Ray fluoroscopy, X-Ray computed tomography (CT), and magnetic resonance imaging (MRI). Examples of regions of interest include blood vessels and organs such as a heart or liver. One category of procedures is referred to as percutaneous (through the skin). In a typical percutaneous procedure, a hollow needle punctures the skin, the needle is inserted, and the tip is positioned in the region of interest. Through the hollow needle, various chemicals may be injected, and various surgical devices may be inserted. For example, in chemotherapy, therapeutic agents are injected into a tumor. In biopsy, a small sample of tissue is removed for laboratory examination.
The success of percutaneous procedures depends strongly on proper insertion of the needle into the region of interest. During insertion, the needle must be properly guided to minimize damage to surrounding tissue and blood vessels. Proper treatment requires precise placement of the tip of the needle. Insertion and placement are controlled primarily by two geometrical factors: the location of the region of interest and the skin entry point for insertion of the needle. The orientation of the needle is defined by the positions of the region of interest and the skin entry point.
In a common procedure, the patient is initially diagnosed with a three-dimensional imaging technique such as C-arm CT or MRI scan. The measurements are digitized and stored as data, often referred to as a “three-dimensional (3-D) volume dataset”. From the 3-D volume dataset, an image processing system may be used later to render various 3-D and two-dimensional (2-D) views to locate a point in the region of interest (for example, a tumor) and a suitable skin entry point. The desired needle trajectory is defined by these two points. During the interventional procedure, the patient is imaged via live X-Ray fluoroscopy, which produces a 2-D projection image on a detector screen. The live 2-D X-Ray fluoroscopy image and the images rendered from the 3-D volume dataset acquired earlier are superimposed on a display to display the proper trajectory along which the needle is to be inserted. A precise method is then required to guide the needle along the intended trajectory. Some prior-art methods may not provide proper precision. Other prior-art methods may require a complicated sequence of steps. Two examples of prior-art methods are described below. Complicated procedures should be avoided because they extend the time during which the patient is subjected to the interventional surgical procedure. What is needed is a simple, quick, and precise method for guiding a needle during insertion in interventional percutaneous procedures.